The long-term objective of this research is to better understand the mechanisms underlying the bonding of bone to calcium-containing substances so that efficacious coatings for joint replacement prostheses can be developed. "Bone bonding" is inferred from: (a) histology and electron microscopy that reveal bone matrix deposited directly on the surface of the calcium-containing implant; and (b) strengths of attachment that cannot be explained by bone apposition alone. The specific research described in this application is intended to test the hypothesis that bone bonding is facilitated by the precipitation of biological apatite onto the calcium-containing implant. This deposition of apatite, similar to the carbonate apatite comprising bone mineral, begins within days of implantation and presumably favors subsequent protein adsorption and bone cell attachment. The investigators postulate that the rate of apatite precipitation and bone formation on calcium-containing substances can be correlated with surface chemistry and crystalline structure, with the most favorable substrate being the one that most closely resembles bone mineral. The applicants hope to show that biological apatite will precipitate onto a metallic surface into which calcium ions have been implanted. They expect that this apatite deposition and subsequent bone bonding proceeds at a slower rate than with calcium phosphates more closely resembling bone mineral. However, the calcium-ion- implanted surface may have mechanical advantages over other substance, warranting its investigation.